Pallet retrieving system

ABSTRACT

A system is disclosed in which a motor driven retriever device brings loaded pallets deposited at a receiving station along a path to an unloading station. If another pallet is already positioned at the unloading platform station, the retriever device deposits its pallet as close thereto as possible. When a pallet is removed from the unloading platform station, pallets positioned therebehind are moved up to fill the void. The details of the pallet retriever device are disclosed showing how mechanical members and electrical switches are combined to provide the system of this invention.

United States Patent [191 Esser et a1.

[54] PALLET RETRIEVING SYSTEM [75] Inventors: George William Esser, WestOrange; Webster W. Jury, Wayne, both of NJ.

[73] Assignee: North American Equipment Corporation, South Hackensack,NJ.

22 Filed: Nov. 18, 1970 21 Appl. No.: 90,543

[52] U.S.Cl. ..198/2l9,2l4/l6 B [51] Int. Cl ..B65g 25/04 [58] Field ofSearch ..198/2l8,21, 19,

198/219; 214/16.1 CD, 38 C, 16 B [56] References Cited UNITED STATESPATENTS Gough ..214/16 B Hanson ..198/21 8 X 1 May 8, 1973 Brown et a1...l98/2l X Larkin 198/21 Primary Examiner-Harvey C. Hornsby AssistantExaminerDouglas D. Watts Attorney-Lerner, David & Littenberg [57]ABSTRACT A system is disclosed in which a motor driven retriever devicebrings loaded pallets deposited at a receiving station along a path toan unloading station. If another pallet is already positioned at theunloading platform station, the retriever device deposits its pallet asclose thereto as possible. When a pallet is removed from the unloadingplatform station, pallets positioned therebehind are moved up to tillthe void. The details of the pallet retriever device are disclosedshowing how mechanical members and electrical switches are combined toprovide the system of this invention.

42 Claims, 32 Drawing Figures J; W 7 l "W M Imp -j I i A l i l 46) I 4?I i i :1 I 1 77 77 l my W Wi mIl' [ll 4: 1' .f/ 45 K Pa tent ed Ma 8,1973 9 Sheets-Sheet 1 BY W, "(9 4104M ATTORNEYS U HM my 3 p \\\nn1 uPatented Ma s, 1973 9 Sheets-Sheet 2 INVENTORS 62 0265- M 55.54

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9 Sheets-Sheet 5 INVENTORS ATTORNEYS Patehted May 1973 9 Sheets-Sheet 4Patented May 8, 1973 9 Sheets-Sheet 5 TA ii BY {pa/m, PM

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ATTORNEYS Patented May 8, 1973 9 Shets-Sheet 9 INVENTORS fdfief M [555?Y 55375? 14 duev Km, paw 24414 ATTORNEYS 1 PALLET RETRIEVING SYSTEMFIELD OF THE INVENTION This invention relates to a system for movingloaded pallets from a receiving station to an unloading platform stationand particularly to a system for moving loaded pallets along aprescribed path.

BACKGROUND OFTHE INVENTION Merchandise stored in warehouses are oftenkept on wooden pallet. When the merchandise is moved within thewarehouse or to an unloading platform, the pallet is moved carrying themerchandise therewith.

One way of moving pallets employes a forklift truck which lifts thepallet and carries it to its new destination. When large numbers ofpallets are to be systematically movedto an unloading platform, the useof aforklift truck to perform the entire taskis not economical. Onereason is that labor cost in such an operation is high. Secondly, when aplurality of pallets are moved to the unloading platform they arestacked one behind the other. When a pallet is unloaded from theunloading platform the remaining pallets stacked behind it must be movedup. This process is time consuming, wastes space and is thereforeexpensive.

As a result thefunction of moving pallets to an unloading platform istypically performed with conveyor systems. Conveyor systems have theadvantage that the pallets move one behind the other and need not becontinuously lifted up and put down. Most conveyor systems use power orgravity to move the pallets. The gravity systems must be mounted on anangle. and therefore take up valuable space which could otherwise beused for warehousing purposes. The conveyor systems used inwarehousesare also quite expensive because when moving heavy merchandisesuch as, for example, refrigerators, the tilted conveyor systems havebreaking devices to prevent the pallets from developing too muchmomentum.

Motor driven continuous conveyor systems for moving goods to anunloading platform in warehouses because the spacing between pallets insuch systems is dependent upon the position of the conveyor when apallet is received thereby. .Therefore,if two pallets are loaded on aconveyor and moved to the unloading platform, the space behind themcannot be filled without bringing those pallets back to the initialpoint.

Systems exist in the prior art for moving objects between predeterminedpoints. Such systems are used for automatic moving of railroad cars andalso for positioning work at work stations on assembly lines. Thesesystems could not be easily adaptedto the moving of pallets for tworeasons. First, they operate on a cueing principle. In other words,objects to be transported are pushed from behind a predetermineddistance. After a first object is pushed the predetermined distance asecond object is placed behind it and pushed the same predetermineddistance thereby cueing one object upon the other. The first objectreaches the end of the line when a sufficient number of objects arepushed in wooden slats having large open areas therebetween. Therefore,sensing and pushing members often employed in the above systems fallbetween the slats into the large spaces indicating to the equipment thatno pallet is there when in fact one is present.

One obstacle to the buildingof a commercially acceptable automatedpallet moving system arises from the nature of warehousing operations.The distance between a pallet receiving station and a loading stationvaries not only from warehouse to warehouse, but also from day to day inthe same warehouse. A successful system must be susceptible of movingpallets between stations of different spacings without the need formajor adjustment.

Therefore, it is an object of this invention to provide a system formoving pallets from a first point in a warehouse to a loading platform.

It is another object of this invention to provide a pallet moving systemwhich requires a minimum of manual operation. I

It is a further object of this invention to provide a palletmovingsystem in which all control functions are directed by switches mountedadjacnet the ends thereof and on a moving carriage so that the length ofthe system can be varied without changes in the operational portionsthereof.

It isstill a further object of this invention to provide a pallet movingsystem which operates in a level position.

It is another object of this invention to provide a pallet moving systemwhich automatically moves the pallets so that they are compactlyarranged adjacent to the unloading platform or are in the process ofbeing so arranged.

It is still another object of this invention to provide a pallet movingsystem which can move pallets made from slats having spacestherebetween.

BRIEF DESCRIPTION OF THE INVENTION With these and other objects in view,the present invention contemplates a system for transporting itemsdeposited at a first station along a path to a second station on thepath. The system will move an item deposited at the first station alongthe path to the second station if another item is not already at thesecond station and to other positions on the path between the first andsecond stations if the other item is present at the second station. Ifan item is present at one of the other positions and none is present atthe second station, the system will transport the item at the oneposition to the second station and individually move any item which isat each of the additional positions closer to thesecond station.

The system is designed to give priority to the moving of items in theintermediate positions to the second station rather than moving of itemsfrom the first station to the second station.

The system is further designed so that the item moving mechanism alwayscomes to rest at the second station when there areno items to be movedand will be activated when an item is placed at the first station orremoved from the second station. The system, how ever, will not attemptto move an item from the first station if all the positions between thefirst and second stations are occupied.

rest position at the second station from the first station a sensor ismounted thereon to enable the mechanism to drop below the items restingon the path when the mechanism approaches the resting items.

DESCRIPTION OF THE DRAWINGS A more complete understanding of theinvention can be had by reference to the following drawings and detaileddescription in which:

FIG. 1 is a top view of a pallet transporting system including atrackway and a carriage constructed in accordance with the teachings ofthis invention;

FIG. 2 is a side view of the system shown in FIG. 1;

FIGS. 3 and 4 are each side views of a front section of the system shownin FIG. 1 specifically showing a lever controlled switching arrangementin two states of operation;

FIG..5 is a sectional view taken along the lines 5-5 in FIG. 2 showingdetails of the construction of the lever arrangements also shown inFIGS. 3 and 4; 7

FIG. 6 is a sectional view taken along the line 6-6 of FIG. 1 showing aproximity sensing mechanism and its mechanical interconnection to a pairof switches employed in the system of this invention for controlling thedirection of movement of the carriage along the trackway;

FIGS. 7 and 8 show the structure shown in FIG. 6 in two different statesof operation;

FIG. 9 is an isometric view of a pallet upon which merchandise istransported in accordance with this invention;

FIG. 10 is an isometric view of the carriage seen in FIG. 1 showing moreclearly the interrelationship of certain mechanical elements;

FIGS. 1 l and 11a are sectional views taken along the lines 11-11,Ila-11a of FIG. 1 showing details of the carriage shown in isometricview in FIG. 10 with mechanical elements in a rest position;

FIGS. 12 and 12a are sectional views analogous to FIGS. 11 and 11arespectively showing the details in a first activated position;

FIGS. 13 and 13a are sectional views analogus to FIGS. 11 and 11arespectively showing the details of the carriage in a second activatedposition;

FIGS. 14 and 14a are sectional views analogous FIGS. 11 and 11arespectively showing the details of the carriage in a third activatedposition;

FIG. 15 is a sectional view taken along the line 15- 15 in FIG. 11showing additional details of the carriage in its rest position;

FIG. 16 is a sectional view taken along the line 16- -16 in FIG. 11showing additional details of the carriage in its rest position;

FIG. 17 is a sectional view taken along the line 17- -ll7 of FIG. 12ashowing additional details of the carriage in its first activatedposition;

FIGS. 18 through 26 show schematically the pallet transporting system ofFIG. 1 in varying slats of operation;

FIG. 27 is a schematic diagram showing the control circuit for operatingthe system shown in FIG. 1; and

FIG. 28 is a side view of a ratchet mechanism employed in one embodimentof this invention.

DETAILED DESCRIPTION OF THE INVENTION Referring now to FIG. 1, we see asystem for transporting merchandise along a path defined by a pair ofchanneled rails 30 and 31. The merchandise is loaded on pallets, such asthe one shown in FIG. 9 and moved between a first station, defined onthe path by a lever switch assembly 32 mounted on the rail 31, and asecond station, defined on the path'by a second lever switch assembly 33also mounted on the rail 31.

A carriage 34 is mounted to ride on wheels 36 through 39 along thechanneled rails 30 and 31. The carriage 34 is driven along the path by amotor 41 which is connected thereto through a drum 42 and a cable 43.The cable 43 is connected to one side of the carriage 34 at an eyelet 44and extends along the path defined by the rails 30 and 31 to a pair ofpulleys 46 and 47. The cable 43 runs from the pulley 47 to and aroundthe drum 42 to a second pair of pulleys 48 and 49. The pulley 49 guidesthe cable 43 back to the second side of the carriage at an eyelet 51. Inthis way, the carriage 34 can be positively driven in both directions bythe motor 41. The length of the cable 43 exposed remains constant byhaving the same amount being taken up on the drum 42 as is being let outtherefrom. It should be noted at this time that the above describedpositive drive mechanism allows one to determine the position of thecarriage 34 by sensing the angular or rotational status of the drum 42.

Referring now to FIGS. 18 through 26, we see in caricature form anillustration of some of the basic functions performed by the system ofthis invention. In FIG. 18, we see in solid lines, the carriage 34 inits normal rest position at the front of the path defined by the rails30 and 31. When a first pallet 52 is placed at the first station definedby the lever switch assembly 32, the carriage 34, in dashed line, issent to engage the pallet 52.

In FIG. 19, we see the carriage 34 about to engage the pallet 52. Whenengagement is made the direction of the carriage 34 is reversed so thatwe see the dashed carriage 34 and pallet 52 going toward the front ofthe path. In FIG. 20, we see that when the carriage 34 reaches the frontof the path it stops, drops the pallet 52 and reverses direction towardsthe first station. If there is a second pallet, as there is in FIG. 20,pallet 53, the carriage 34 (see FIG. 21) brings the pallet 53 to restbehind the pallet 52. The carriage 34 then reverses direction to lookfor additional pallets at the first station if a new pallet has beenplaced at the first station. In FIG. 21, we see the carriage 34 going topickup the third pallet 54. FIG. 22 shows that after the carriage 34travels to the first station and finds no pallet then it comes to restat the front of the path.

FIGS. 23 through 26 show that the carriage 34 will be activated by theremoval of the pallet 52 (see FIG. 23) from the second station, definedby the lever switch assembly 33, to individually move the pallets 53,55, and 56 to fill the void left by the removal of the pallet 52. Thecarriage 34 will continue to move the pallets up to fill the void untilno pallet remains on the path. Then the carriage 34 will travel passedthe first position and return to assume its normal rest position at thefront of the path.

The system is further configured to cancel a work assignment of bringingpallets from the first station as shown in FIGS. 18 through 22if apallet is removed from the second station while a second pallet reststherebehind creating a void at the front of the path. This is preferableto having the system stack pallets from the first position behind a rowof pallets with a void there in front. Otherwise, it would be necessaryfor the carriage 34 to move all the pallets on the path to fill the voidafter the first station was freed of pallets increasing the number oftrips which the carriage 34 would make to move all the pallets adjacentto the front of the path.

The above functions are achieved in the preferred embodiment of thisinvention through the interrelationship of electrical circuitry andmechanical elements. It should be understood, however, that many of thefunctions performed by the circuitry could be performed by mechanicalelements while some of the functions performed by the mechanicalelements could be performed by circuitry.

The circuitry shown in FIG. 27 operates the motor 41 (starting, stoppingand reversing the same) in response to seven switches interconnectedmechanically with the mechanical structure. The seven switches can belooked upon as three groups. The first group includes two switches. Oneis contained in the lever switch assembly 32 while the second iscontained in the lever switch assembly 33. These switches are employedto actuate the system in response to pallets being placed or removed atthe first or second station respectively. The second group of switches(see FIGS. 6, 7, and 8) include switches 57 and 58 which ultimatelysense the carriage 34 coming into a predetermined proximity with apallet or other properly configured item on the path. The third group ofswitches includes three switch assemblies 59, 61, and 62 for sensingpredetermined positions of the carriage 34 by monitoring the rotationalcondition of the drum 42 (for example, by counting the number ofrotations thereof from a predetermined rest position).

The first and second groups of switches are activated through mechanicalinteractions particularly suited for motor driven retriever devices. Anexample of the first group of switches which includes the lever switchassemblies 32 and 33 is seen in FIGS. 2, 3, 4 and 5. The lever switchassembly 33 includes a lever plate 63 affixed to the channel 31 by apair oflugs 64 and 66. The lugs 64 and 66 are fixedly seeded in thechannel 31. The lugs 64 and 66 protrude through slots 67 and 68 in thelever plate 63. A pair of spring members 69 and 71 urge the lever plate63 upwardly into the path. A switch element 72 is mounted in fixedrelationship to the channel 31 to be actuated by a member 73 whichprotrudes from the lever plate 63.

The lever plate 63 defines the second station by being situated so thata pallet which is brought to the end of the path will have a back endthereof resting in the middle of the lever plate 63. In a like manner,the lever plate on the lever switch assembly defines the first stationin that pallets placed on the first station will be rested with thefront end thereof halfway onto the lever thereof. When the lever plate63 has no pallet thereon as shown in FIG. 2, the springs 69 and 71 urgethe lever plate 63 upward. In this position, the switch 72 provides anormally opened contact. If the lever plate 63 is urged downwardly bypallets either on the front portion further pressing downward on theswitch 72 or on both sides thereof also pressing downward on the switch72, the switch 72 will still provide the normally opened contact. If,however, a pallet is absent from the front portion of the lever plate 63and present on the back portion thereof, the spring 71 will be depressedpushing the back portion of the lever plate 63 downwardly and pivotingthe lever plate 63 around the lug 64 urging the front end of the leverplate 63 upward away from the switch 72 to close the contact therein.The lever switch assembly 33 therefore will operate to provide a closedcontact only when a pallet is present at the next to the last positionon the path and no pallet is present at the second station. In a likemanner, the lever switch assembly 32 will provide a closed contact onlywhen a pallet is present at the first station and no pallet is presentat the posiiton immediately adjacent thereto.

It should be noted that in this way, the mechanical elements includingthe lever plate 63 pivoted on the channel 31 and urged upwardly by thesprings 69 and 71 provide a logical function which could be performed bya less complicated mechanical. structure and more complex electroniccircuitry. This mechanical combination is capable of sensing the absenceof a pallet on the front of the lever plate 63 and the presence of oneon the back end. This combination of absence on the front and presenceon the back is the only conditions which will activate the switch 72..It should be noted that a single pivot point could logically perform thesame function but would not be as mechanically stable. The relativestrength of the springs 69 and 71 would then come into play to determineif the switch 72 were in fact in an opened or closed position.

The second group of switches 57 and 58 are operated by a pivotedactuator 73 (see FIGS. 6, 7, 8 and 10) 81 takes up the portion of theguy wire 77 between the rollers 78 and 79. A cam 82 rotatably mounted onthe carriage 34 by a shaft 80 holds the pivoted roller 81 inpredetermined positions dependent upon the angular position thereof. Thetension of the guy wire 77 is initially adjusted so that if the pivotedcam member 82 is as shown in FIG. 6, the finger 83 on the actuator 73will not contact either of the switches 57 or 58 It should be noted thatthe distance from the pivot point of cam 82 is larger to the left sidethereof than to the right and the distance from the pivot point to thesurface varies continuously therebetween.

Therefore, in FIG. 7 when the cam 82 is rotated in a counterclockwisedirection the left side thereof raises the roller 81 increasing thetension on the guy wire 77 The increase tension pivots the actuator 73so that the finger 83 thereof operatesjthe switch 58. In a like manner,when the cam 82 is rotated in a clockwise direction, see FIG. 8, thetension in the guy wire 77 is reduced so that the finger 83 thereofoperates the switch 57.

Referring now to FIGS. 1 and 10, to see details of the carriage 34, wesee that the wheels 36 through 38 and 39 are mounted on shafts 84 and86. The carriage 34 includes a pair of contacting assemblies 87 and 88joined together by a center plate 89. Each of the contacting assemblies87 and 88 carry a contacting shoe 91 and 92 respectively. The contactingshoes 91 and 92 ride on roller carrying arms which are positioned by cammembers. For example, the contacting shoe 92 rides on roller carryingarms 93 and 94 which are positioned by cam members 96 and 97. The cammembers 96 and 97 which position the roller arms 93 and 94 and the cammembers which position the roller arms of the cam members not shown aremounted on and moved by a pair of shafts 98 and 99 respectively. Theunderside of the contacting shoes 91 and 92 which engage the roller armshave wedged shaped members 101 and 102 connected thereto extendingdownwardly and to the left.

Referring now to FIG. 1 1, we see a view taken through the center of thecontacting shoe 92 to show in more detail the carriage in its normal orrest position. A spring 103 biases the contacting shoe 92 in therighthand direction so that it rides up on the roller arms 92 and 93 anda portion thereof extends above the rails 30 and 31. A downwardlyextending flange 104 on the underside of the contacting shoe 92 resetsagainst an angle plate 106 mounted on the carriage 34 to limit therightward movement of the shoe 92.

The spring 103 is a relatively weak spring having only sufficientstrength to lift the weight of the contacting shoe 92 up and to theright as it pulls the contacting shoe 92. Therefore, if the carriage 34as seen in FIG. 1 1 were moved to the right; the edge of the contactingshoe 92 extending above the rail 31 would be stopped by the pallet 53resting on the rails 30 and 31. As the carriage 34 continued to travelto the right, the contacting shoe 92 would remain stationary relative tothe path but move leftwardly relative to the carriage 34 thus sinkingdownwardly as the roller arms 93 and 94 move under the'surface 102. Whenthe contacting shoe 92 had dropped below the pallet 53, it would thenagain move with the carriage 34 under the pallet 53 against the bottomside thereof. Each time frictional forces between the upper surface ofthe shoe 92 and the bottom surface of the pallets 53 would tend to stopthe rightward movement of the shoe 92; the shoe 92 would again drop suffciently to move again with the carriage. Therefore, one can see that asort of slight jerking motion would occur as the shoe 92 slid under thepallet 53.

If the direction of the carriage 34 were reversed when the carriage 34was under the pallet 53 (see FIG. 13) the rollers of the roller arms 93and 94 would push against the surfaces 102. Since the spring 103 drawsthe contacting shoe 92 upwardly and to the right, the contacting shoe 92will be pressing against the underside of the pallet 53. As the carriage34 attempted to move to the left and carry the contacting shoe 92therewith, the frictional forces between the pallet 53 and thecontacting shoe 92 would be sufficient so that the contacting shoe 92would attempt to pull the pallet 53 therewith. The pallet 53, however,will rest on the rails 30 and 31 and would tend to impede the forwardmovement of the shoe 92 due to the frictional forces between the pallet53 and the rail 31.

Therefore, as the carriage 34 begins its motion to the right the rollerbearing arms 93 and 94 will push against the surfaces 102 tending toraise the pallet 54 slightly off the rails 30 and 31. The raising of thepallet 53 off the rails will substantially reduce the amount of forcenecessary to move the pallet 53 forward and will therefore result ineasy transport of the pallet 53 slightly above the rails 30 and 31.

It has been found that the above arrangement is sufficient to transportpallets carrying relatively light loads thereon, for example in therange of pounds. The pallet 53 will alternately rise up off the rails 30and 31 and then as a steady state motion is achieved, be touched backdown on the rails. At this point frictional forces will again developwhich will again raise the pallet 53 up off the rails.

It has been further found, however, that with heavie loads, for examplein the range of 1,500 pounds, the touching down of the pallet 53 willtend to cause wear on the rails 30 and 31 as well as produce a bumpingaction. Therefore, in one embodiment of this invention a ratchetmechanism (see FIG. 28) is incorporated in the contacting assemblies 87and 88 to hold the shoes 91 and 92 respectively at their highest mostpoint of rise after being under the pallet 53. The ratchet mechanismholds the shoe 91 and 92 up until they are otherwise disengaged from theunderside of the pallet 53.

The ratchet, seen in FIG. 28, has three principal parts. The ratchetmechanism itself includes a fixed ratchet element 107, fixedly securedto the carriage 34 cooperating with a pivoted ratchet element 108,pivotally secured to the shoe 92 by a shoulder screw 109. A ratchetspring 111 biases the pivotally mounted ratchet element 108 against thefixed ratchet element 107. A release bar 112 pivotally mounted on theshoe 92 and having a hold down pin 114 thereon is biased by a releasebar spring 113 to normally hold down the pivoted ratchet element 108 outof engagement with the fixed ratchet element 107. It should beunderstood that a similar ratchet mechanism would be employed on thecarriage 34 to hold the shoe 91.

The release bar 112 has a contact surface 116 which extends above thetop of the shoe 92 when holding the pivoted ratchet element 108 out ofengagement with the fixed ratchet element 107. When the carriage 34moves under a pallet 53 as described with respect to FIGS. 11 to 13, theunderside of the pallet 53 pushes against the contact surface 116raising the hold down pin 1 14 and allowing the ratchet spring 1 1 1 tobring the pivoted ratchet element 108 into engagement with the teeth onthe fixed ratchet element 107. As the carriage 34 reverses direction asshown in FIG. 13 to raise the pallet 53 under the shoe 92 off the rails30 and 31, the pivoted ratchet element 102 advances along the teeth ofthe fixed ratchet element 107 holding the shoe 92 in its uppermostposition.

It should be clear that the ratchet will not release until the contactsurface 116 on the release bar is allowed to rise up above the top ofthe contact shoe 92 pushing the pivoted ratchet member 108 out ofengagement with the fixed ratchet member 107.

The carriage 34 is configured to drop the shoes 91 and 92 out ofengagement with the underside of the pallet 53 when the carriage 34encounters a pallet or other item such as the front of the path havingcharacteristics such as a pallet at the left side thereof. The carriage34 (see FIG. 10) has a sensor arm 117 securely fastened to the shaft 80.A sensor head 118 is secured to the sensor arm 117. In addition torotating the cam member 82 for providing electrical signals in the formof contact openings and closures in the switches 57 and 58, the sensorarm 117 and sensor head 118 carries a sensor linkage 119 therewith. Aspring 121 (see FIGS. 1 and 10) positions the sensor arm 117 into itsnormal rest position.

FIG. 11a is a sectional view showing the sensor arm 117, sensor head 118and the sensor linkage 119, and additional linkages operative therewithin their normal rest position. The sensor linkage 119 has a slottedsection at the right end thereof 122. A pivoted cam follower 123pivotally mounted on the shaft 98 has a pin 125 thereon to ride in theslot 122 of the linkage 119. The cam follower 123 is pivotally connectedto a connecting linkage 124 which drives a follower member 126 to rotatethe shaft 99 to essentially the same position maintained by the shaft98.

Referring now to FIGS. 12 and 12a, we see that when the carriage 34rides under the pallet 53, the sensor head 118 rotates the sensor arm117 in a counterclockwise direction when contact is made between thepallet 53 and the sensor head 118. This rotates the cam member 82 toactuate the switch 58 and to drive the sensor linkage 119 to the left.The sensor linkage 119 (see particularly FIG. 12a) when moving to theleft does not transmit any movement to the cam follower 123 but ratherslides in the slot 122 thereof.

Referring now to FIGS. 14 and 14a, we see that when the sensor head 118engages a pallet 53 or the like when the carriage 34 is moving from leftto right, the sensor head 118 in addition to rotating the shaft 80 ac- Ituating the switch 57, pushes the sensor linkage 119 to the rightpushing the cam follower 123 in counterclockwise direction. The motionof the cam follower 123 is reflected in the linkage 124 rotating themember 126 and therefore the shaft 99. In FIG. 14, we see that the camelements 96 and 97 carried by the shafts 98 and 99 respectively rotatetherewith allowing the roller arms 93 and 94 respectively to dropremoving the shoe 92 from engagement with the underside of the pallet53. This will, of course, release the ratchet so that the spring 103 canbring the shoe 92 to the position shown in FIG- 14.

Looking now at FIGS. 9 and 10, we can see that the pallet 53 isconstructed from spaced-apart slats 128. It has been found that thesensing head 118 may fall between the slats 128 or if a pallet 53 has abroken or missing slat, the sensing head 118 will rise up in the middleof the pallet 53 engaging the shoes 91 and 92 at a time when in factthey should be disengaged from the pallet 53.

In accordance with this invention, to overcome this problem, a latchmechanism seen in FIGS. 10, 11a, 12a, 13a, 14a, 16 and 17 has beenincorporated. When the sensing head 118 contacts a pallet when moving ina leftwardly direction as shown in FIG. 14, a latching arm 129 engagesthe center plate 89 holding the linkage 124 and all the elementsattached thereto to the right against the force of springs 131 and 132(seen clearly in FIG. 1) even if the sensing head 118 should encounter aspace on the underside of the pallet 53. A

I0 latch release member 133 is carried by a latch release plate 134 (seeparticularly FIGS. 10, 16 and 17). The latch release plate 134 ispivotally mounted on the carriage 34 on a bracket 136. A latch releasespring 137 urges the latch release plate 134 upwardly so that the latchrelease member 133 can engage the latch linkage 129 lifting it off thecenter plate 89 allowing the springs 131 and 132 (see FIG. 1) to returnthe linkages 124 and the elements carried therewith to their normal restposition shown in FIG. 11a.

A latch bar 138 is attached to the top side of the latch hold down plate134. When the carriage 34 begins to go under a pallet 53 (see FIG. 16)one of the curved portions of the latch bar 138 slides under the palletand is thereby cammed downwardly to depress the latch release plate 134and the latch release member 133 therewith compressing the spring 137.So long as the bar 138 is in contact with the underside of the pallet53, the latch linkage 129 will not be released notwithstanding the factthat the sensing head 118 is no longer in contact with the underside ofthe pallet 53. When, however, the bar 138 is no longer under the pallet53, indicating that the carriage 34 is completely away from the pallet53, the spring 137 will push up the latch release plate 134 lifting upthe latch release member 133 to disengage the latch linkage 129 from thecenter place 89 allowing the springs 131 and 132 to return the linkagesto their normal rest position;

Referring now to all the Figures and particularly to FIG. 27, we see acontrol circuit 133. The control circuit 133 controls the motor 41 whichmoves the carriage 34 along the path defined by the rails 30 and 31 inresponse to predetermined patterns of pallets arranged thereon. Themovements of the carriage 34 dictated by the logic built into thecontrol circuit 133 enables the mechanical features described above tocooperate with each other and with pallets to compactly arrange palletsdeposited near the lever switch assembly 32 adjacent to the front of thepath.

The control circuit 133 is shown in FIG. 27 with all contacts in thepositions they occupy when the carriage is at rest at the front of thepath. When the carriage is at rest at the front of the path is depressedto the right (see FIGS. 14 and 14a) under a shelf type member 134 whichdefines the front of the path.

The control circuit 133 operates off both AC and DC voltages. The ACvoltage is supplied on a pair of leads 136 and 137. The DC voltage issupplied between a lead 137 and a lead 138. Lead 138 is positive withrespect to the lead 137. A diode 139 connecting the lead 136 to the lead138 rectifies the AC voltage. A capacitor 141 filters the rectified ACvoltage to supply the positive voltage on the lead 138 with respect tothe lead 137.

In operation when a pallet is placed in the first position on the path,as defined by the right half portion of the lever switch assembly 32, anormally opened contact 32a is closed applying power to the coil of arelay Z through a normally closed contact 59a of the limit switch 59.Energization of the relay Z closes a'normally opened contact Z 1. Theclosing of the contact Z -1 energizes the coil of a relay Z through anormally closed contact DIS-1 of a relay DIS.

The energization of the relay Z,,,, closes two normally opened contactsZ -J and Z,,,,-2. The closing of the Z,,,,-1 contact supplies DC powerto a relay coil B,,,,,. The B contacts (not shown) apply power to acircuit (not shown) for energizing the motor 41. The closing of the L -2contact applies AC power to the contacts 57a and 58a associated with theswitches 57 and 58 to determine the direction in which the powersupplied by the 13 relay will drive the motor 41.

Since the pallet is at the front of the path with the sensing headdepressed to the right, the tension is decreased in the guy wire 77 sothat the contact 57a will be closed. Therefore, the closing of theZ,,,,-2 relay applies power to a latch C coil of a latch relay.

The energization of the latch C coil opens normally closed contactslatch-1 and latch-2 while closing a normally opened contact latch-3. Theopening of the latch-2 contact de-energizes an OP,- relay coil andcloses an OP relay coil. The OP, relay coil operates contacts (notshown) for energizing the motor 41 to operate in reverse while the OP,coil operates contacts (not shown) for operating the motor 41 in aforward direction. Forward operation of motor 41 is to be understood asoperation which would drive the carriage 31 towards the end of the pathadjacent to the lever switch assembly 32 while a reverse operation ofthe motor will be understood to mean one which would operate the motor41 to drive the carriage 34 towards the end of the path adjacent to thelever switch assembly 33.

A pair of delay circuits 142 and 143 are interposed between the contactslatch-2 and latch-3 and the relay coils OP, and OP, respectively toprovide approximately a one second delay between the time one of therespective OP relays opens its contacts and the other closes itscontacts. This is in order to allow the motor 41 to come to a naturalstop before power is supplied thereto to drive it in its oppositedirection.

When the motor 41 begins to turn the drum 42 taking up and letting outthe cable 43, the carriage 34 proceeds from the end of the path adjacentthe shelf 134 towards the pallet resting on the lever switch assembly32. When the carriage moves away from the shelf 134, the contact 58a isopened so that now both the contacts 57a and 58a are opened. The latchrelay, however, will maintain the state of its contacts untilenergization is applied to the coil latch C At the same time a normallyclosed contact 61-a opens and a normally opened contact 61-b closes inresponse to rotation of the drum 42 beyond a predetermined limitposition. The closing of the contact 61-b now provides a parallel pathwith the contact Z,,,,l to hold the relay coil B energized.

When the sensing head 118 on the carriage 34 engages the pallet restingon the lever switch assembly 32 as shown in FIG. 12, the cam 82increases the tension on the guy wire 77 operating the switch 58 toclose the contact 58a actuating the coil latch C of the latch relayagain closing the contacts latch-1 and latch 2 and opening the contactlatch-3. The opening of the contact latch-3 de-energizes the relay OPwhile the closing of the latch-2 contact energizes the relay OP, therebyreversing direction of the motor 41 after a one second delay.

The carriage 34 then moves to the left (see FIG. 13) restoring thesensor head to its normal rest position thereby restoring normal tensionto the guy wire 77 so that the contacts 57a and 58a are both open andbringing the pallet up off the rails 30 and 31 to move with the carriage34. When the carriage 34 passes a position defined by the switch 59, thecontact 59a will be opened.

The limit switches 59 and 62 are configured so that the limit switch 59will only be operated when the carriage is moving from the right to theleft as shown in FIG. 1. The opening of the limit switch contact 59adeenergizes the relay 2, opening the contact Z l deenergizing the relayZ thereby opening the contacts Z,,,,l and Z,,,,2.

The opening of the contact Z,,,,2 renders the contacts 57a and 58aunable to effect the state of the latch relay. The opening of thecontact Z,,,,l has no immediate effect because it is bypassed by thelimit switch contact 61-b holding the B relay energized so that themotor 41 will continue to drive the carriage 34 towards the front of thepath.

When the sensor head 118 contacts the pallet resting at the front of thepath, the carriage 34 will assume the state shown in FIGS. 14 and 14a.As discussed above the decreased tension in the guy wire 77 will closethe contact 57a. Since, however, the Z,,,,'2contact is now opened theclosing of the contact 57a will not alter the direction of the carriage34. The sensing head 118, however, will be effective to drop the shoes91 and 92 to a position where they are unable to engage the pallet sothat the carriage 34 will ride under the pallet at the end of the pathand continue to move forward until the limit switch operates opening thecontact 61b removing power from the B, relay.

From the above, it is seen that the system as thus far described willrespond to pallets being deposited at a first position defined by thelever switch assembly 32 to energize the carriage 34 for traveling downthe path until contact with a pallet is made. When contact is made, thecarriage 34 will reverse direction and bring the pallet to the front ofthe path. It should also be clear that if a pallet was already stationedat the front of the path the carriage would deposit the palletimmediately adjacent thereto. When the carriage 34 encounters either thefront of the path or a pallet the carriage disengages from the palletand reverses its direction to search out additional pallets on the pathif another pallet has already been placed at the first position. If nomore pallets are no the path, the direction reversing circuitry beingrendered inoperative will allow the carriage 34 to travel under thepallets adjacent to the front end of the path and come to a restposition at the front of the path.

If the system is at rest with two or more pallets resting adjacent tothe shelf 134 and the pallet immediately adjacent to the shelf 134 isremoved, the lever switch assembly 33 will close a contact 33a. Thecontact 33a will energize the Z coil through the normally closed contact59a of the limit switch 59, the contact 33a, diode 142 and the contact61a of the front limit switch 61. The energization of the relay Z willpull in the holding contact 2 -1 as above described and therefore renderthe system again operative. The carriage 34 will then travel rightwardlydown the path until a pallet is encountered. In this case, the firstpallet encountered will be the one resting on the lever switch assembly33. The carriage 34 would bring this pallet to the front of the path andthen continue as above described traveling down-the path and retrievingpallets until one final trip is made in which the carriage 34 reachesthe point defined by the switch 59. If no pallet is resting at the firstposition the carriage 34 will be reversed by operation of the limitswitch 62. The carriage 34 will then travel under the pallets restingadjacent to the front of the path and come to rest adjacent to the shelf134.

If the carriage 34 is down towards the righthand end of the pathbringing pallets to the left from the first station as defined by thelever switch assembly 32 and a pallet resting immediately adjacentthereto, the control circuit 133 will cancel the work being done at therighthand end of the path the next time the carriage is moving to theleft if not already moving to the left. The carriage will then bebrought to the shelf 134 immediately beginning to move the adjacentpallets up before returning to the righthand end of the path to bringnew pallets down the path.

This is accomplished by a relay designed RR which is in series with thelatch-l contact. The latch-l contact is opened when the carriage ismoving to the left on the path. A normally closed contact RR 1 is inseries with a relay coil of the DIS relay. Therefore, when the contact33a of the lever switch assembly 33 is closed while the Z l contact isclosed a path is developed from the lead 137 through the 2 -1 contact,the contact 33a, a diode 143, the RR-1 contact and the coil of the DISrelay to the lead 136. The diode 143 provides rectification so that theDIS relay can be energized in an opposite polarity from the remaining DCcircuitry. A capacitor 144 filters the DC provided by the diode 143.Operation of the DIS relay opens the DIS-l contact and closes the DIS-2contact. The opening of the DIS-1 contact de-energizes the Z relayopening contacts Z,,,,l and l -2.

As discussed above the opening of the.Z,,,,-2 contact renders thedirection changing circuitry of the system inoperative so that thecarriage 34 under power of that supplied to the contact 61b and the Erelay drives the carriage 34 to the shelf 134. When the carriage 34arrives at the shelf 134, the contact 61b opens removing power from themotor 41 and closes the contact 61a.

The closing of the contact 61a re-energizes the Z,,,, relay through theDIS-2 contacts and a diode 146. Reenergization of the Z,,,, relay bringsback in the contact Z,,,,2 which operates the latch-C, coil through thecontact 57a which opens the RR-l contact so that the DIS-2 contact isopened and the DIS-Icontact is again closed bringing this circuit backto its above described operating procedure. It is seen that in this way,the system will retrieve pallets left at a first position to fill a voidwhen it occurs at the second position andwill cancel an assignment ofmoving pallets from the first position towards the second position whena void is created at the second position.

An additional feature of this invention which is inherent from theconfiguration above described is that the system will not be energizedto retrieve pallets if the entire path is filled. If pallets are placedon both sides of the lever switch assembly 32 indicating that palletsare filling the entire path, the switch 32 near the contact 32a will notbe energized so that the carriage 34 will not move from its restposition under the shelf 134.

It should be understood that while this invention has been describedwith respect to a specific embodiment thereof, numerous others willbecome obvious to those of ordinary skill in the art in light of thisdisclosure.

What is claimed is:

1. A mechanism for transporting items, left at a first station, to asecond station; said mechanism including:

an item transporting carriage mounted for movement along a path, saidpath including said first and second stations, said carriage beingengageable with said items for moving said items when moving towardssaid second station and being disengaged from said items when movingtowards said first station;

means responsive to a first control signal for moving said carriagetowards said first station and to a second control signal for movingsaid carriage towards said second station;

means responsive to an item resting at said first station for providinga first item signal; means on said carriage for sensing the proximity ofan item when said carriage is moving along said path towards said firststation to provide a first sensing signal;

means on said carriage for sensing the proximity of at item when saidcarriage is moving along said path towards said second station toprovide a second sensing signal; and

means rendered effective by said first item signal responsive to saidfirst and second sensing signals for providing said first and secondcontrol signals.

2. The mechanism as defined in claim 1 also includ' ing:

means responsive to said carriage being present at a first position onsaid path;

means responsive to said carriage being at said second station forproviding a second station signal; and

means rendered effective by said first limit signal responsive to saidsecond station signal for dis abling said first and second controlsignal providing means.

3. The mechanism as defined in claim 2 in which said first limit signalalso renders said first and second control signal providing meansnon-responsive to said first and second sensing signal.

4. The mechanism as defined in claim. 3 in which said item transportingcarriage includes:

means for engaging said items as said carriage moves from said firststation to said second station; and means responsive to said secondsensing signal for rendering said engaging means inoperative.

5. The mechanism as defined in claim 4 in which said first and secondcontrol signal providing means normally provides said first controlsignal.

6. The mechanism as defined in claim Sin which said first and secondcontrol signal providing means provides said second control signal inresponse to said first sensing signal and said first control signal inresponse to said secondsensing signal.

7. The mechanism as defined in claim 6 also including:

means responsive to said carriage being present at a second position onsaid path, said second position being beyond said first position whenlooking from said second station, for providing a second limit signal;and

said first and second control signal providing means is furtherresponsive to said second limit signal for providing said second controlsignal.

8. The mechanism as defined in claim 1 also including:

means responsive to an item resting adjacent to said second station forproviding a second item signal; and

said first and second control signal providing means is renderedeffective by either said first or second item signals. 9. The mechanismas defined in claim 8 also including:

means responsive tosaid carriage being present at a first position onsaid path, said first position being beyond said first station whenlooking from said second station, for providing a first limit signal;

means responsive to said carriage being at said second station forproviding a second station signal; and

means rendered effective by said first limit signal responsive to saidsecond station signal for disabling said first and second control signalprovidmg means.

10. The mechanism as defined in claim 9 in which said first limit signalalso renders said first and second control signal providing meansnon-responsive to said first and second sensing signal.

11. The mechanism as defined in claim 10 in which said item transportingcarriage includes:

means for engaging said items as said carriage moves from said firststation to said second station; and means responsive to said secondsensing signal for rendering said engaging means inoperative.

12. The mechanism as defined in claim 11 in which said first and secondcontrol signal providing means normally provides said first controlsignal.

13. The mechanism as defined in claim 12 in which said first and secondcontrol signal providing means provides said second control signal inresponse to said first sensing signal and said first control signal inresponse to said second sensing signal.

14. The mechanism as defined in claim 13 also including:

means responsive to said carriage being present at a second position onsaid path, said second position being beyond said first position whenlooking from said second station, for providing a second limit signal;and

said first and second control signal providing means is furtherresponsive to said second limit signal for providing said second controlsignal.

15. The mechanism as defined in claim 8 in which said first and secondcontrol signal providing means is rendered non-responsive to said firstand second sensing signals by the simultaneous occurrence of said secondcontrol signal and said second item signal.

16. The mechanism as defined in claim 15 in which said item transportingcarriage includes:

means for engaging said items as said carriage moves from said firststation to said second station; and means responsive to said secondsensing signal for rendering said engaging means inoperative.

17. The mechanism as defined in claim 16 also including:

means responsive to said carriage being present at a first position onsaid path, said first position being 5 beyond said first station whenlooking from said second station, for providing a first limit signal;means responsive to said carriage being at said second station forproviding a second station signal; and

10 means rendered effective by said first limit signal responsive tosaid second station signal for disabling said first and second controlsignal providing means.

l5 18. The mechanism as defined in claim 17 in which said first limitsignal also renders said first and second control signal providing meansnon-responsive to said first and second sensing signal.

19. The mechanism as defined in claim 18 in which said first and secondcontrol signal providing means normally provides said first controlsignal.

20. The mechanism as defined in claim 19 in which said first and secondcontrol signal providing means provides said second control signal inresponse to said first sensing signal and said first control signal inresponse to said second sensing signal.

21. The mechanism as defined in claim 20 also in cluding:

means responsive to said carriage being present at a second position onsaid path, said second position being beyond said first position whenlooking from said second station, for providing a second limit signal;and

said first and second control signal providing means is furtherresponsive to said second limit signal for providing said second controlsignal.

22. A mechanism for transporting items, left at a first station, to asecond station; said mechanism including:

an item transporting carriage mounted for movement along a path, saidpath including said first and second stations, said carriage beingengageable with said items for moving said items when moving towardssaid second station and being disengaged from said items when movingtowards said first statron;

means responsive to a first control signal for moving said carriagetowards said first station and to a second control signal for movingsaid carriage towards said second station; means responsive. to an itemresting adjacent to said second station for providing a second itemsignal;

means on said carriage for sensing the proximity of an item when saidcarriage is moving along said path towards said first station to providea first sensing signal;

means on said carriage for sensing the proximity of an item when saidcarriage is moving along said path towards said second station toprovide a second sensing signal; and

means rendered effective by said second item signal responsive to saidfirst and second sensing signals for providing said first and secondcontrol signals.

23. The mechanism as defined in claim 22 also including:

means responsive to said carriage being present at a first position onsaid path;

means responsive to said carriage being at said second station forproviding a second station signal; and

means rendered effective by said first limit signal responsive to saidsecond station signal for disabling said first and second control signalprovidmg means.

24. The mechanism as defined in claim 23 in which said first limitsignal also renders said first and second control signal providing meansnon-responsive to said first and second sensing signal.

25. The mechanism as defined in claim 24 in which said item transportingcarriage includes:

means for engaging said items as said carriage moves from said firststation to said second station; and means responsive to said secondsensing signal for rendering said engaging means inoperative.

26. The mechanism as defined in claim 25 in which said first and secondcontrol signal providing means normally provides said first controlsignal.

27. The mechanism as defined in claim 26 in which said first and secondcontrol signal providing means provides said second control signal inresponse to said first sensing signal and said first control signal inresponse to said second sensing signal.

28. The mechanism as defined in claim 27 also including:

means responsive to said carriage being present at a second position onsaid path, said second position being beyond said firstposition whenlooking from said second station, for providing a second limit signal;and

said first and second control signal providing means is furtherresponsive to said second limit signal for providing said secondcontrolsignal.

29. In a mechanism for transporting items:

means for defining a path upon which said items may be transported;

a pivot plate;

means for movably mounting said pivot plate in pivotal and limitedtranslational relationship to said path;

means for urging said pivot plate into said path;

means for sensing the position of a portion of said pivot plate toindicate a predetermined pattern of items on said path adjacent to saidpivot plate to provide a first item signal;

an item transporting carriage mounted for movement along said path;

means responsive to a first control signal for moving said carriage in afirst direction along said path and to a second control signal formoving said carriage in a second direction along said path; meansrendered effective by said first item signal for providing said firstand second control signal;

means on said carriage for sensing the proximity of an item when saidcarriage is moving along said path in said first direction to provide afirst sensing signal;

means on said carriage for sensing the proximity of an item when saidcarriage is moving along said path in said second direction to provide asecond sensing signal; and

said first and second control signal providing means is responsive tosaid first and second sensing signals.

30. In a mechanism as defined in claim 29 in which said carriage isengageable with said items for moving said items when moving insaidfirst direction and is dis engaged from said items when moving in saidsecond direction.

31. A mechanism for transporting items; said mechanism including:

an item transporting carriage mounted for movement along a path;

means responsive to a control signal for moving said carriage along saidpath; a guy wire extending along said path, said guy wire normally beingunder a predetermined tension;

means mounted on said carriage for sensing the proximity of itemsto saidcarriage to alter the tension on said guy wire; and

means responsive to said tension on said guy wire for generating saidcontrol signal.

32. The mechanism as defined in claim 31 also including:

means responsive to an item resting at a predetermined position on saidpath for generating an item signal; and

said control signal generating means is rendered effective by said firstitem signal.

33. The mechanism as defined in claim 32 in which said item signalgenerating means includes:

a pivot plate;

means for movably mounting said pivot plate in pivotal and limitedtranslational relationship to said path;

means for urging said pivot plate into said path; and

means for sensing the position of a portion of said pivot plate toindicate a predetermined pattern of items on said path thereby providessaid item signal, said predetermined pattern including an item restingat said predetermined position on said path.

34. The mechanism as defined in claim 31 in which said means responsiveto said tension. on said guy wire includes:

an actuator member mounted for pivotal motion around a point fixed withrespect to said path; means for applying a pivoting force to pivot saidactuator member;

means for connecting said guy wire to said actuator member to balancesaid pivoting force; and

means responsive to said pivotal. position of said actuator member toprovide an indication of said tension on said wire.

35. The mechanism as defined in claim 34 also including:

means responsive to an item resting at a predetermined position on saidpath for generating an item signal; and

said control signal generating means is rendered effective by said firstitem signal.

36. The mechanism as defined in claim 35 in which said means responsiveto said tension on said guy wire includes:

an actuator member mounted for pivotal motion around a point fixed withrespect to said path; means for applying a pivoting force to pivot saidactuator member;

means for connecting said guy wire to said actuator member to balancesaid pivoting force; and

means responsive to said pivotal position of said actuator member toprovide an indication of said tension on said wire.

37.-In a system for transporting an item:

means for defining a path, said path defining means having a surfacealong said path for supporting said item; said surface defining asupporting region thereabout;

a carriage mounted for movement along said path, said movement of saidcarriage being adjacent to but not intersecting with said region;

item engaging means movably mounted on said carriage for simultaneouslimited movement (1) into and out of said region and(2) along said pathrelative to said carriage;

means for biasing said item engaging means into said region;

means for sensing the proximity of said item as said carriage moves in afirst direction on said path to withdraw said item engaging means fromsaid region; and

ratchet means responsive to said item engaging means engaging an itemfor holding said item engaging means in said path, said ratchet meansbeing released by operation of said sensor means.

38. In a system for transporting an item:

means for defining a path, said path defining means having a surfacealong said path for supporting said item; said surface defining asupporting region thereabout;

a carriage mounted for movement along said path, said movement of saidcarriage being adjacent to but not intersecting with said region;

item engaging means movably mounted on said carriage for simultaneouslimited movement (1) into and out of said region and (2) along said pathrelative to said carriage;

means for biasing said item engaging means into said region;

said item is transported from a first station on said path to a secondstation on said path, and said item engaging means is mounted to movetowards said first station relative to said carriage as said itemengaging means moves into said region, said system also including:

means responsive to a first control signal for moving said carriagetowards said first station and to a second control signal for movingsaid carriage towards said second station; 5 means responsive to an itemresting at said first station for providing a first item signal, andmeans rendered effective by said first item signal for providing saidfirst and second control signal. 39. In the system as defined in claim47 in which said item signal providing means includes:

a pivot plate; means for movably mounting said pivot plate in pivotaland limited translational relationship to said path; means for urgingsaid pivot plate into said region;

and means for sensing the position of a portion of said pivot plate toindicate a predetermined pattern of items on said path thereby providingsaid item signal.

40. n the system as defined 1n clalm 39 also including:

means on said carriage for sensing the proximity of said item when saidcarriage is moving along said path towards said first station to providea first sensing signal; means on said carriage for sensing the proximityof an item when said carriage is moving along said path towards saidsecond station to provide a second sensing signal; and

said first and second control signal providing means is responsive tosaid first and second sensing signal. 41. In the system as defined inclaim in which said second sensing signal withdraws said item engagingmeans from said region.

42. In the system as defined in claim 41 also includmg:

a guy wire extending along said path, said guy wire normally being undera predetermined tension; and

1. A mechanism for transporting items, left at a first station, to asecond station; said mechanism including: an item transporting carriagemounted for movement along a path, said path including said first andsecond stations, said carriage being engageable with said items formoving said items when moving towards said second station and beingdisengaged from said items when moving towards said first station; meansresponsive to a first control signal for moving said carriage towardssaid first station and to a second control signal for moving saidcarriage towards said second station; means responsive to an itemresting at said first station for providing a first item signal; meanson said carriage for sensing the proximity of an item when said carriageis moving along said path towards said first station to provide a firstsensing signal; means on said carriage for sensing the proximity of atitem when said carriage is moving along said path towards said secondstation to provide a second sensing signal; and means rendered effectiveby said first item signal responsive to said first and second sensingsignals for providing said first and second control signals.
 2. Themechanism as defined in claim 1 also including: means responsive to saidcarriage being present at a first position on said path; meansresponsive to said carriage being at said second station for providing asecond station signal; and means rendered effective by said first limitsignal responsive to said second station signal for disabling said firstand second control signal providing means.
 3. The mechanism as definedin claim 2 in which said first limit signal also renders said first andsecond control signal providing means non-responsive to said first andsecond sensing signal.
 4. The mechanism as defined in claim 3 in whichsaid item transporting carriage includes: means for engaging said itemsas said carriage moves from said first station to said second station;and means responsive to said second sensing signal for rendering saIdengaging means inoperative.
 5. The mechanism as defined in claim 4 inwhich said first and second control signal providing means normallyprovides said first control signal.
 6. The mechanism as defined in claim5 in which said first and second control signal providing means providessaid second control signal in response to said first sensing signal andsaid first control signal in response to said second sensing signal. 7.The mechanism as defined in claim 6 also including: means responsive tosaid carriage being present at a second position on said path, saidsecond position being beyond said first position when looking from saidsecond station, for providing a second limit signal; and said first andsecond control signal providing means is further responsive to saidsecond limit signal for providing said second control signal.
 8. Themechanism as defined in claim 1 also including: means responsive to anitem resting adjacent to said second station for providing a second itemsignal; and said first and second control signal providing means isrendered effective by either said first or second item signals.
 9. Themechanism as defined in claim 8 also including: means responsive to saidcarriage being present at a first position on said path, said firstposition being beyond said first station when looking from said secondstation, for providing a first limit signal; means responsive to saidcarriage being at said second station for providing a second stationsignal; and means rendered effective by said first limit signalresponsive to said second station signal for disabling said first andsecond control signal providing means.
 10. The mechanism as defined inclaim 9 in which said first limit signal also renders said first andsecond control signal providing means non-responsive to said first andsecond sensing signal.
 11. The mechanism as defined in claim 10 in whichsaid item transporting carriage includes: means for engaging said itemsas said carriage moves from said first station to said second station;and means responsive to said second sensing signal for rendering saidengaging means inoperative.
 12. The mechanism as defined in claim 11 inwhich said first and second control signal providing means normallyprovides said first control signal.
 13. The mechanism as defined inclaim 12 in which said first and second control signal providing meansprovides said second control signal in response to said first sensingsignal and said first control signal in response to said second sensingsignal.
 14. The mechanism as defined in claim 13 also including: meansresponsive to said carriage being present at a second position on saidpath, said second position being beyond said first position when lookingfrom said second station, for providing a second limit signal; and saidfirst and second control signal providing means is further responsive tosaid second limit signal for providing said second control signal. 15.The mechanism as defined in claim 8 in which said first and secondcontrol signal providing means is rendered non-responsive to said firstand second sensing signals by the simultaneous occurrence of said secondcontrol signal and said second item signal.
 16. The mechanism as definedin claim 15 in which said item transporting carriage includes: means forengaging said items as said carriage moves from said first station tosaid second station; and means responsive to said second sensing signalfor rendering said engaging means inoperative.
 17. The mechanism asdefined in claim 16 also including: means responsive to said carriagebeing present at a first position on said path, said first positionbeing beyond said first station when looking from said second station,for providing a first limit signal; means responsive to said carriagebeing at said second station for providing a second station signal; andmeans rendered effective by said first limIt signal responsive to saidsecond station signal for disabling said first and second control signalproviding means.
 18. The mechanism as defined in claim 17 in which saidfirst limit signal also renders said first and second control signalproviding means non-responsive to said first and second sensing signal.19. The mechanism as defined in claim 18 in which said first and secondcontrol signal providing means normally provides said first controlsignal.
 20. The mechanism as defined in claim 19 in which said first andsecond control signal providing means provides said second controlsignal in response to said first sensing signal and said first controlsignal in response to said second sensing signal.
 21. The mechanism asdefined in claim 20 also including: means responsive to said carriagebeing present at a second position on said path, said second positionbeing beyond said first position when looking from said second station,for providing a second limit signal; and said first and second controlsignal providing means is further responsive to said second limit signalfor providing said second control signal.
 22. A mechanism fortransporting items, left at a first station, to a second station; saidmechanism including: an item transporting carriage mounted for movementalong a path, said path including said first and second stations, saidcarriage being engageable with said items for moving said items whenmoving towards said second station and being disengaged from said itemswhen moving towards said first station; means responsive to a firstcontrol signal for moving said carriage towards said first station andto a second control signal for moving said carriage towards said secondstation; means responsive to an item resting adjacent to said secondstation for providing a second item signal; means on said carriage forsensing the proximity of an item when said carriage is moving along saidpath towards said first station to provide a first sensing signal; meanson said carriage for sensing the proximity of an item when said carriageis moving along said path towards said second station to provide asecond sensing signal; and means rendered effective by said second itemsignal responsive to said first and second sensing signals for providingsaid first and second control signals.
 23. The mechanism as defined inclaim 22 also including: means responsive to said carriage being presentat a first position on said path; means responsive to said carriagebeing at said second station for providing a second station signal; andmeans rendered effective by said first limit signal responsive to saidsecond station signal for disabling said first and second control signalproviding means.
 24. The mechanism as defined in claim 23 in which saidfirst limit signal also renders said first and second control signalproviding means non-responsive to said first and second sensing signal.25. The mechanism as defined in claim 24 in which said item transportingcarriage includes: means for engaging said items as said carriage movesfrom said first station to said second station; and means responsive tosaid second sensing signal for rendering said engaging meansinoperative.
 26. The mechanism as defined in claim 25 in which saidfirst and second control signal providing means normally provides saidfirst control signal.
 27. The mechanism as defined in claim 26 in whichsaid first and second control signal providing means provides saidsecond control signal in response to said first sensing signal and saidfirst control signal in response to said second sensing signal.
 28. Themechanism as defined in claim 27 also including: means responsive tosaid carriage being present at a second position on said path, saidsecond position being beyond said first position when looking from saidsecond station, for providing a second limit signal; and said first andsecond control signal providing meAns is further responsive to saidsecond limit signal for providing said second control signal.
 29. In amechanism for transporting items: means for defining a path upon whichsaid items may be transported; a pivot plate; means for movably mountingsaid pivot plate in pivotal and limited translational relationship tosaid path; means for urging said pivot plate into said path; means forsensing the position of a portion of said pivot plate to indicate apredetermined pattern of items on said path adjacent to said pivot plateto provide a first item signal; an item transporting carriage mountedfor movement along said path; means responsive to a first control signalfor moving said carriage in a first direction along said path and to asecond control signal for moving said carriage in a second directionalong said path; means rendered effective by said first item signal forproviding said first and second control signal; means on said carriagefor sensing the proximity of an item when said carriage is moving alongsaid path in said first direction to provide a first sensing signal;means on said carriage for sensing the proximity of an item when saidcarriage is moving along said path in said second direction to provide asecond sensing signal; and said first and second control signalproviding means is responsive to said first and second sensing signals.30. In a mechanism as defined in claim 29 in which said carriage isengageable with said items for moving said items when moving in saidfirst direction and is disengaged from said items when moving in saidsecond direction.
 31. A mechanism for transporting items; said mechanismincluding: an item transporting carriage mounted for movement along apath; means responsive to a control signal for moving said carriagealong said path; a guy wire extending along said path, said guy wirenormally being under a predetermined tension; means mounted on saidcarriage for sensing the proximity of items to said carriage to alterthe tension on said guy wire; and means responsive to said tension onsaid guy wire for generating said control signal.
 32. The mechanism asdefined in claim 31 also including: means responsive to an item restingat a predetermined position on said path for generating an item signal;and said control signal generating means is rendered effective by saidfirst item signal.
 33. The mechanism as defined in claim 32 in whichsaid item signal generating means includes: a pivot plate; means formovably mounting said pivot plate in pivotal and limited translationalrelationship to said path; means for urging said pivot plate into saidpath; and means for sensing the position of a portion of said pivotplate to indicate a predetermined pattern of items on said path therebyprovides said item signal, said predetermined pattern including an itemresting at said predetermined position on said path.
 34. The mechanismas defined in claim 31 in which said means responsive to said tension onsaid guy wire includes: an actuator member mounted for pivotal motionaround a point fixed with respect to said path; means for applying apivoting force to pivot said actuator member; means for connecting saidguy wire to said actuator member to balance said pivoting force; andmeans responsive to said pivotal position of said actuator member toprovide an indication of said tension on said wire.
 35. The mechanism asdefined in claim 34 also including: means responsive to an item restingat a predetermined position on said path for generating an item signal;and said control signal generating means is rendered effective by saidfirst item signal.
 36. The mechanism as defined in claim 35 in whichsaid means responsive to said tension on said guy wire includes: anactuator member mounted for pivotal motion around a point fixed withrespect to said path; means for applying a pivoting force to pivot saidactuator member; means for connecting said guy wire to said actuatormember to balance said pivoting force; and means responsive to saidpivotal position of said actuator member to provide an indication ofsaid tension on said wire.
 37. In a system for transporting an item:means for defining a path, said path defining means having a surfacealong said path for supporting said item; said surface defining asupporting region thereabout; a carriage mounted for movement along saidpath, said movement of said carriage being adjacent to but notintersecting with said region; item engaging means movably mounted onsaid carriage for simultaneous limited movement (1) into and out of saidregion and (2) along said path relative to said carriage; means forbiasing said item engaging means into said region; means for sensing theproximity of said item as said carriage moves in a first direction onsaid path to withdraw said item engaging means from said region; andratchet means responsive to said item engaging means engaging an itemfor holding said item engaging means in said path, said ratchet meansbeing released by operation of said sensor means.
 38. In a system fortransporting an item: means for defining a path, said path definingmeans having a surface along said path for supporting said item; saidsurface defining a supporting region thereabout; a carriage mounted formovement along said path, said movement of said carriage being adjacentto but not intersecting with said region; item engaging means movablymounted on said carriage for simultaneous limited movement (1) into andout of said region and (2) along said path relative to said carriage;means for biasing said item engaging means into said region; said itemis transported from a first station on said path to a second station onsaid path, and said item engaging means is mounted to move towards saidfirst station relative to said carriage as said item engaging meansmoves into said region, said system also including: means responsive toa first control signal for moving said carriage towards said firststation and to a second control signal for moving said carriage towardssaid second station; means responsive to an item resting at said firststation for providing a first item signal, and means rendered effectiveby said first item signal for providing said first and second controlsignal.
 39. In the system as defined in claim 47 in which said itemsignal providing means includes: a pivot plate; means for movablymounting said pivot plate in pivotal and limited translationalrelationship to said path; means for urging said pivot plate into saidregion; and means for sensing the position of a portion of said pivotplate to indicate a predetermined pattern of items on said path therebyproviding said item signal.
 40. In the system as defined in claim 39also including: means on said carriage for sensing the proximity of saiditem when said carriage is moving along said path towards said firststation to provide a first sensing signal; means on said carriage forsensing the proximity of an item when said carriage is moving along saidpath towards said second station to provide a second sensing signal; andsaid first and second control signal providing means is responsive tosaid first and second sensing signal.
 41. In the system as defined inclaim 40 in which said second sensing signal withdraws said itemengaging means from said region.
 42. In the system as defined in claim41 also including: a guy wire extending along said path, said guy wirenormally being under a predetermined tension; and said first and secondsensing signal providing means alters the tension on said guy wire totransmit said first and second sensing signals to said first and secondcontrol signal providing means.